


Sibilance

by Cypress_Leaves



Category: Undertale (Video Game)
Genre: Alternate Universe - Dreamtale (Undertale), Alternate Universe - Dusttale (Undertale), Alternate Universe - Horrortale (Undertale), Alternate Universe - Killertale (Undertale), Alternate Universe - Lamiatale (Undertale), Alternate Universe - Underfell (Undertale), Alternate Universe - Underswap (Undertale), Angst, Angst and Hurt/Comfort, Angst with a Happy Ending, Eventual Fluff, Eventual Happy Ending, Hurt/Comfort, Implied/Referenced Rape/Non-con, Lamia Nightmare - Freeform, M/M, Multi, Multiple Universes Colliding, Non-Consensual Body Modification, Non-Consensual Bondage, Non-Consensual Drug Use, Non-Consensual Groping, Non-Consensual Touching, Non-Graphic Rape/Non-Con, Other Additional Tags to Be Added, Rape Recovery, Recovery, Slow To Update, Tags May Change, Trauma, Whump
Language: English
Status: In-Progress
Published: 2020-11-29
Updated: 2020-11-28
Packaged: 2021-03-10 07:39:49
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,589
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27729646
Author URL: https://archiveofourown.org/users/Cypress_Leaves/pseuds/Cypress_Leaves
Summary: sib·i·lant –making or characterized by a hissing sound."his sibilant whisper"
Relationships: Bad Sanses Poly, Nightmare/Killer/Dust/Horror
Comments: 1
Kudos: 48





	Sibilance

Nightmare carefully stepped out of the shadows into the throne room of the Swapfell copy. The atmosphere was dark and chilly, more so than it should have been; he almost scoffed at this. It was often a gamble on the kind of reception he would receive when visiting different Fellverses to work out details of their pledged loyalty to him. Based on the papers he’d been working on in regards to this universe, he hadn’t been expecting this, yet it didn’t necessarily surprise him.

  


“ **You have made a mistake,** ” he called out, confidently striding to the center of the room. “ **However, I am willing to overlook this error in your judgment, if you would be so kind as to promise this won’t happen again.** ”

  


He waited patiently for the Toriel of this world to show herself, making an effort to keep his tentacles smooth and calm in their idle movements. Though this _was_ an annoyance to him and his plans, it was not a major one, nor was it the first he’d ever dealt with. He truly was willing to overlook this, anyway. He didn’t blame the inhabitants of Fellverses for taking precautions.

  


With his superb night vision, it wasn’t hard to immediately notice the large, furred form that rose from behind the throne. Pleased, he allowed his teeth to curl in a smile, adjusting his tentacles to create a makeshift chair for him to relax on. “ **Thank you. Now, for us to proceed –** ”

  


The room was suddenly illuminated with bright light. He hissed, his socket squeezing shut as he physically recoiled from the burning sensation the light elicited.

  


For a moment, he crouched there, dazed; what the hell had happened? Nothing like this had ever occurred before; the light _hurt_ , his goop rippling and near boiling, almost reminiscent of the sensation caused by Dream’s positivity arrows.

  


In his split-second of vulnerability, he heard the Toriel call out, “Now!”

  


The light flared, the burn increasing to nearly unmanageable levels.

  


His eyelight rolled back into his skull, then flickered, disappearing and leaving his socket void as his body collapsed.

  


* * *

  


Nightmare woke with a jolt, his socket snapping open and eyelight flaring into being. Reflexively, he moved to stand up quickly, only to find he was unable to, the sound of rattling chains echoing eerily in the darkness. He gritted his teeth, exhaling loudly as he forced himself to relax and take stock of the situation.

  


His eyelight dimmed, snuffing out nearly all light in the room, allowing his eyesight to better adjust to the darkness. Formless shapes sharpened quickly. His gaze flicked around; he looked to be in some kind of damp cell made primarily out of stone. His wrists and ankles were chained, spread out in such a way that he couldn’t move except to turn onto his side from his stomach.

  


Testingly, he went to move his tentacles, only to find that they _weren’t there_.

  


He jerked his skull around to peer at his back. Something rubbed against his cervical vertebrae. He hesitated, his whole body stilling.

  


_…No way…_

  


Slowly, Nightmare looked inward, reaching for the magic that would allow him to resummon his tentacles –

  


Electricity, at a much higher voltage than he’d expected, lanced through his body from his neck.

  


He almost swore he could smell a faint ozone scent before he blacked out.

  


* * *

  


When he was conscious again, the first thing he noticed was his position had changed.

  


Rather than laying spread out on the floor, he was now being held upright. He glanced up; his wrists were held up above his head in a way that made his arms lift straight up, his feet barely touching the ground. He squirmed, then stilled with a sudden rush of cold fear when his back collided with something furred. A chuckle resounded through the room from behind him.

  


“‘e’s awake,” a husky voice called out. “We were told no last’n’ harm, yeah?”

  


“Yeah,” someone else replied. Footsteps approached from behind. “We can mess around with him a bit as long as we don’t scratch up his bones, mostly. Here.”

  


Liquid sloshed behind his head before clawed fingers gripped his chin, pressing into the sides of his mandible. He jerked and hissed as his mouth was forced open, ready to snarl out a dozen insults when a small bottle was pushed between his teeth and its contents dumped into his mouth. The fingers released his jaw and were quick to hold his mouth closed. A thumb lifted, covering his nose.

  


“C’mon, Nightmare,” the first voice murmured next to where his ears would’ve been if he were human. “Swallow it. It’ll be easier fer all of us.”

  


His teeth sharpened as he tried to bite the monster’s hand, but he found himself unable to with the angle they were covering his mouth at. When he began to feel light-headed, something rubbed at the bottom of his chin, then his top cervical vertebra above the magic suppression collar; he swallowed instinctively, sputtering and coughing when the hand was removed.

  


“That wasn’t so hard, hm,” the monster whispered.

  


“F–fuck you,” Nightmare snarled, licking his teeth. He froze, suddenly, his eyelight constricting. His tongue was summoned. The monster laughed behind him as they trailed their claws down his ribcage. His body was starting to feel heated, his magic stimulated by an outside force. “What the hell did you do?”

  


The monster didn’t answer, just let their hand drift down towards his legs. “Such pretty cyan yer magic is,” they murmured. Nightmare cast a glance down; his magic was, indeed, starting to summon, shapeless cyan mist swirling over his bones. It was already solidifying at his chest, where the monster’s other hand was resting, claws idly tracing his breasts.

  


“Damn, it’s working fast, huh?” the second monster chimed in, circling Nightmare. He stared at the feline, his teeth slightly parted, his eyelight shrunk down to a shaky pinprick as the monster behind him pressed up against his back after his ecto had formed a solid shape over his upper body. Faintly, he was aware that his bones were rattling, the chains holding his arms up softly clinking together.

  


He inhaled sharply and squeezed his socket shut when the feline prowled closer, their hands reaching for his pelvic girdle.

  


* * *

  


Nightmare’s exhale shuddered as the cell’s door closed with a _thunk!_. He sagged, his wrists the only things supporting his weight, and desperately wished that the monsters could’ve at least adjusted his bonds so he could curl up into a ball on the floor.

  


He tried to reach for his magic to dissipate his full-body ecto-skin, but his efforts were for naught; whatever drug or aphrodisiac he’d been forced to consume hadn’t yet worn off. He shivered when cool air brushed against his false flesh, latching onto the sensation.

  


Anything to ignore the sticky cyan, red, and purple magics staining his thighs.

  


* * *

  


He refused to let himself sleep, even when exhaustion was tugging at his socket. Memories flickered at the edges of his consciousness each time he let his eye close, jolting him back to full awareness, almost expecting the monsters to be back in the cell with him.

  


After a while – a few hours later, maybe, but it felt like much longer – he began to hear snippets of conversation outside the cell.

  


“…ready yet?”

  


“…ost, maybe in…w hours…”

  


“…work?”

  


“It sh…some…imula…n…get…venom prod…ng…”

  


There was a lull in the conversation, then,

  


“We c’n get some more time with ‘im, then, hm?”

  


“Yeah, if you want. It’s not been long enough yet for his magic to have faded.”

  


Nightmare’s gaze latched onto the door when keys jangling sounded. He jerked backward when it was pushed open, the feline slinking into the room, closely followed by the canine. Their clothes were already off.

  


“Hey, Nightmare,” the cat monster purred, slitted eyes glinting in the darkness. “Ready for some more?”

  


“D’ya need more of that ‘phrodisiac?”

  


He closed his eye, his body trembling, feeling utterly powerless as he tried his best to disconnect from the situation.

  


* * *

  


The next time the monsters came into the cell, they had their clothes on. The feline was holding a syringe, filled to the brim with dark blue liquid. Nightmare eyed it warily, but he couldn’t find the strength to flinch away when the monster moved closer, their empty hand gripping onto his collar.

  


The needle was inserted smoothly into the magic covering his neck, the tip pushing into the space between his atlas and axis cervical vertebrae. His breath came out as a harsh exhale when the liquid in the syringe was pushed out, swiftly distributing through his system.

  


He could distinctly feel the liquid’s progress through his body; when it reached his legs, he twitched, not expecting the pain that washed over his femurs. His ecto shifted, then started to pull his thighs together.

  


“Damn, it’s really working,” the feline muttered, eyes wide as they watched his legs. Nightmare twitched again, then felt himself start writhing as his false skin stitched together, his magic spreading down rapidly to lengthen. His bones creaked inside his flesh.

  


“Knock ‘im out,” the canine snapped. “‘e’ll hurt ‘imself at this rate, we need this t’happen smoothly.”

  


Another syringe was fished out of the cat’s pocket. The liquid inside was quickly inserted into Nightmare’s magic.

  


The world faded away into pain and darkness.

  


* * *

  


Consciousness was incredibly slow to return to him. When he finally managed to open his socket, he stiffened immediately.

  


Something felt…wrong.

  


He wasn’t chained anymore; he was laying on his front, skull turned to the side and cushioned by his arms. His ecto seemed to have dissipated, but there was still a cyan glow in the room that would suggest otherwise.

  


Shakily, he pushed himself up with his arms, not noticing the way his tongue, now thin with a forked tip, was flicking out past his teeth as he looked around. The monsters were gone, and he really _wasn’t_ chained up. He moved to stand, only to discover his legs had changed.

  


Socket wide as he remembered what had happened last time he’d been conscious, he twisted around onto his back, staring at the long cyan tail that now replaced his legs.

  


He felt cold and empty as he trailed his gaze down along it and the coils it had formed, then looked back up it, seeing the way the ecto dissipated once it reached the bottom of his ribcage.

  


What the hell had those monsters done to him?

  


Hesitantly, he reached out to touch the tail, almost trying to convince himself that it wasn’t his. When his phalanges made contact with it, however, he felt it clearly, as though it was just one of his tentacles. Now that he was focusing, he also felt the chill of the damp stone floor biting into the scales.

  


He parted his jaws as though to say something, then hesitated, taking notice of his summoned tongue. Experimentally, he flicked it out his mouth, finally noticing the feedback it was giving him. It was almost like…smelling, he compared it to. He pulled it back into his mouth, poking at his larger, sharper canines, then the magic pouches at the roof of his mouth behind the fangs.

  


_Venom. Hadn’t one of them said something about venom?_

  


The situation was nearly amusing in its ridiculousness. He’d been kidnapped, raped, and turned into a venomous half-snake hybrid. He barely managed to fight off the hysteria, carefully lowering himself back down to the floor. Without really being aware of it, he turned back onto his front, his tail squirming until it was sloppily coiled around him.

  


With nothing better to do, Nightmare waited silently for the monsters to return.

  


* * *

  


It was almost unreasonably difficult to try to move his tail manually, but it seemed to have no qualms about doing things on its own. It curled around the legs of the feline currently holding him up with their arms hooked under his, one hand clamped over the front of his collar. The other was pressed against his forehead, holding his skull back against the cat’s shoulder. He twisted and squirmed, trying to get away, but they had a strong grip on him.

  


“Alright, come on,” they instructed their companion, holding his skull more firmly. Nightmare hissed loudly when the canine came into view, holding a bottle-shaped bowl with a thin layer of latex stretched over the top. Just looking at it made his newly-acquired fangs and venom glands tingle.

  


“Y’sure ‘e can’t move?”

  


“ _Yes_ , I’m sure. Hurry up.”

  


“A’ight…” they eyed him warily before moving closer. The hand on his collar lifted to his chin, fingers digging into his mandible reminiscent of when he’d been forced to drink the aphrodisiac. He hissed again, tongue flicking the air as his mouth was opened. The monster holding the bowl quickly moved it underneath his fangs, handling it carefully. He tried to jerk his head away, but he couldn’t move any further back with the shoulder behind his skull.

  


“ _Hurry up_ ,” the feline behind him snapped again irritatedly.

  


“Shut up,” the canine retorted, though they did seem to listen to the order, pushing the bowl up so Nightmare’s fangs penetrated the latex. They moved it up further so the edge of it rubbed his venom glands to stimulate them, as Nightmare had no interest in biting down on it himself.

  


An embarrassing noise left his mouth when a few drops of cyan-tinted venom dripped into the bowl, his eyelight fuzzing and rolling back into his head as his whole body shuddered.

  


“Holy shit,” the monster holding the bowl laughed, turning it slowly so it continued to coax his venom out. “It is fuckin’ arousin’ to ‘im?”

  


Another sound, somewhat like a whimper, slipped past his defenses when the dog’s free hand brushed up his tail, teasing along his underbelly. He squirmed, but the action was half-hearted; he wasn't able to focus with the way his head was fogging up, soft _drip-drip-drip_ s echoing in the cell.

  


* * *

  


When the monsters finally left, he took comfort in the way he could hug his tail to his chest, burying half of his face against the scales.

  


He felt strangely violated, in a way that was almost worse than when the monsters had raped him, taking advantage of the effects of the aphrodisiac to bring him to orgasm.

  


He hadn’t even known getting his venom milked could seem like such an intimate thing. He shuddered and held his tail tighter as he remembered the way he’d been crying out, vocalizing his pleasure as he’d experienced a pseudo-orgasm at the end of the milking.

  


Desperately, he hoped it wouldn’t happen again.

  


* * *

  


His wishes seemed to have been pointless, since the monsters returned constantly to take more of his venom – his sense of time was quickly becoming skewed, but the milking seemed to occur once a day. Each one was just as embarrassing as the first. After the fifth time, he tried to distract himself from the process by remembering his times in bed with his boyfriends, ranging from Killer’s intense, praise-filled domination to Horror’s gentle, servitude control, but eventually, he had the sense that he was beginning to taint happy recollections. He felt even dirtier afterward, especially when he remembered how the desperation-laced noises he made got uncomfortably close to sounding like his boys’ names.

  


The only good thing about his situation, at this point, was that the monsters didn’t directly molest him again. The milkings were scarily similar, but regardless, this fact was the only thing he could latch onto for comfort.

  


He’d tried many a time to bite the monsters; so far, he’d only gotten close once, but his jaws had been pried open almost as soon as he’d dug his teeth into the cat's furred arm, leaving no time for him to have injected his venom.

  


Most days, he attempted to try learning to move his tail. It was frustratingly difficult; despite being his, made directly of his magic, the muscles seemed disconnected from his soul, and the most he could do was twitch the tip. Annoyingly, when he _wasn’t_ focusing on it, his tail seemingly loved to move about, coiling around itself or his body, or latching onto the feline holding him during the venom milking sessions.

  


He learned quickly that talking was incredibly difficult. Though magic played a big part in a skeleton monster’s ability to speak, this seemed to have changed after he’d been transformed. The magic used for speaking had shifted into something else (he wondered briefly if it had been diverted to maintaining his venom glands, deciding that was the most reasonable option), leaving him mostly reliant on his tongue, which was much too long and thin to properly articulate. Most of his attempts at speaking left him aggravated and resorting to hissing, a much easier sound to make.

  


After about a week, he decided he would need to try focusing his efforts on how to escape this place. If he didn’t, he doubted his life would change much from the routine the monsters had settled into.

  


* * *

  


On what he guessed was the forty-third day was when Nightmare was ready to set his plan into motion.

  


Throughout the whole time there, he’d been taking notice of how the monsters entered the cell, how quick they were to handle his biting attempts, and at which speed they moved depending on what he was doing.

  


He’d come to the conclusion that an escape attempt would best be performed by immediately attacking the feline when they came through the door, using their body to trip the dog, biting both of them just to be safe, then fleeing the room and closing the door behind him. He’d already been working on how to deal with his collar, and after days of frequently toying with it, he’d managed to wear it down enough to cut through it to take it off. Once the cell door was shut, he’d be able to claw the collar off, then open a portal to leave.

  


He’d had his plan formed for a few days, but each time the monsters had entered the cell, sudden anxiety would seize him, freezing his body until his chance had slipped away. This time, he was determined to follow through.

  


Ever since waking up, he’d been crouched just next to the door, pressed against the wall. He used his tongue frequently to scent the air; he’d learned before that he could smell the monsters nearing for about a minute before they got to the cell.

  


When he detected the smoky traces of their smell, his whole body stiffened, but he refused to let his fear paralyze him once more. Unconsciously, a finger tapped out the seconds against the stone floor, waiting with bated breath for the moment the keys would jangle and the door would open.

  


_Tap…_

_  
_

_Tap…_

_  
_

_Tap…_

_  
_

_Tap…_

_  
_

_Tap…_

  


His finger stilled when he sensed more than heard the footsteps approaching the door. His eyelight slitted, a sudden predatory instinct washing over him, as the keys clinked together.

  


The door opened.

  


He pounced, launching himself forward with his arms, digging his teeth into the cat monster’s unprotected leg. A muffled shriek sounded overhead as he injected his venom, pulling back with a satisfied hiss when the noise died down and the cat’s body loosened. They collapsed back against their companion, who stumbled with the suddenness of their full weight being in their arms. With an ease that would suggest it was practiced, Nightmare let his focus divert entirely from his tail. The tip of it lashed forward, wrapping around the unparalyzed dog’s right ankle. They tripped when they tried to drag the feline backward, falling onto their rump.

  


Using his arms to move along the ground, Nightmare dove forward, sinking his fangs into the canine’s lower arm. They jerked, trying to shove him away, but quickly went entirely limp just seconds after his venom was injected.

  


He could sense how close he was to escape now; frantically, he turned to shove the two monsters further into the cell, then latched onto the edge of the doorway, pulling himself out of the room. He gripped one hand on the door next, using his other to pull his tail closer, shoving the cell’s door shut and fumbling briefly with the lock.

  


He curled his fingers into the most worn part of the collar’s surface, scratching at it until it started to rip and, finally, fell off of him.

  


His breaths came out as harsh pants as he gave a full-body shudder, his bones tingling and sparking with the sudden rush of the return of his magic, his tail wiggling bonelessly as the glow of the gelatinous ecto it was made of brightened considerably. What was supposed to be a murmured chant of _‘fuck’_ s came out instead as a wavering hiss that eventually disintegrated into a loud purr.

  


It had worked.

  


The relief that he felt at that moment was enough to leave him dizzy and light-headed. He could’ve sworn he was about to pass out. It took a moment for that thought to register, but when it did, he reached for his newly returned magic, creating a portal in the shadows.

  


He didn’t even focus on where it would take him before he dragged himself through it. Anything to get away from this place.

  


He found himself collapsing in a pile of snow, and this time, the relief _was_ enough for him to pass out.


End file.
